Methods of manufacturing combination thrust-bearing and radial bearing apparatuses

ABSTRACT

Embodiments of the invention relate to bearing apparatuses in which one bearing surface of the bearing apparatus includes diamond, while another bearing surface includes a non-diamond superhard material (e.g., silicon carbide). For example, a bearing apparatus may include a bearing stator assembly and a bearing rotor assembly. The bearing stator assembly and bearing rotor assembly each include a support ring and one or more superhard bearing elements generally opposed to one another. The bearing surface(s) of the rotor or stator may include diamond, while the bearing surface(s) of the other of the rotor or stator do not include diamond. Another bearing apparatus may include both thrust- and radial bearing components. The generally opposed thrust-bearing elements may include diamond, while the generally opposed radial bearing elements may not include diamond, but include a non-diamond superhard material, such as silicon carbide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/826,121 filed on 13 Aug. 2015, which is a division of U.S.application Ser. No. 13/792,778 filed on 11 Mar. 2013 (issued as U.S.Pat. No. 9,127,708 on 8 Sep. 2015), the disclosure of each of theforegoing applications is incorporated herein, in its entirety, by thisreference.

BACKGROUND

Wear-resistant, polycrystalline diamond compacts (“PDCs”) are utilizedin a variety of mechanical applications, including bearing apparatuses.For example, the bearing apparatuses may be thrust-bearing apparatusesor radial bearing apparatuses.

Bearing elements included in such bearing apparatuses may comprise a PDCtypically including a superhard polycrystalline diamond (“PCD”) layercommonly known as a diamond table. The diamond table is formed andbonded to a substrate using a high-pressure/high-temperature (“HPHT”)process. The PDC bearing element may be brazed into a preformed pocket,socket, or other receptacle formed in a bearing support ring.

Despite the availability of a number of different bearing apparatusesincluding such PDCs, manufacturers and users of bearing apparatusescontinue to seek bearing apparatuses that exhibit improved performancecharacteristics, lower cost, or both.

SUMMARY

Embodiments of the invention relate to bearing apparatuses including abearing stator assembly and a bearing rotor assembly. The bearing statorassembly and bearing rotor assembly each include a support ring and oneor more superhard bearing elements, with each of the one or moresuperhard bearing elements including a respective bearing surface. Thebearing surfaces of the bearing stator assembly and bearing rotorassembly are generally opposed to one another. The bearing apparatus isspecifically configured so that the bearing surface(s) of the rotor andthe bearing surface(s) of the stator include different materials. Forexample, the bearing surface(s) of one of the rotor or stator mayinclude diamond (e.g., polycrystalline diamond), while the bearingsurface(s) of the other of the rotor or stator may not include diamond,but may include a non-diamond superhard material (e.g., silicon carbide)or another type of material such as a diamond-silicon carbide composite.

Such configurations advantageously provide bearing apparatuses that maybe manufactured at lower cost, as compared to configurations that employPCD bearing surfaces on both generally opposed bearing surfaces. Inaddition to reduced initial cost, additional benefits of such aconfiguration may include that the rotor or stator that does not includediamond may wear preferentially, so as to fail or otherwise wear outbefore the other of the rotor or stator that does include diamond. Thenon-diamond rotor or stator may be replaced at significantly lower costthan replacement of the entire bearing apparatus (i.e., both rotor andstator) where both rotor and stator bearing surfaces comprise diamond.Failure of the non-diamond bearing surface(s) may advantageously notresult in damage to downstream equipment such as valves or othercomponents that would be damaged by failure of a diamond bearingsurface.

In addition, diamond bearing surfaces exhibit significantly higherthermal conduction than other superhard materials, such as siliconcarbide. Because of this difference, use of silicon carbide or similarnon-diamond superhard materials for both stator and rotor bearingsurfaces may not allow sufficient heat transfer away from the bearingsurfaces for practical use in some applications. Use of a diamond rotoror stator with a silicon carbide or other non-diamond superhard materialfor the other of the rotor or stator may provide improved heat transferaway from the silicon carbide or other non-diamond superhard materialbearing surface. Thus, while use of non-diamond superhard material forboth stator and rotor bearing surfaces may not be practical in someapplications, use of a diamond and non-diamond bearing surfaces for thestator and rotor may overcome such thermal management problems.

In an embodiment, a bearing apparatus may include a thrust-bearingassembly and a radial bearing assembly in which the bearing surfaces ofboth the stator and rotor of the thrust-bearing assembly includediamond, and the bearing surfaces of both the stator and rotor of theradial bearing assembly do not include diamond, but comprise anothersuperhard material (e.g., silicon carbide). For example, such athrust-bearing assembly may include a thrust-bearing stator and athrust-bearing rotor, each including a stator support ring and one ormore superhard bearing element(s). The superhard stator and rotorthrust-bearing element(s) each include respective superhardthrust-bearing surface(s) that are generally opposed to one another. Theradial bearing assembly may include a radial bearing stator and a radialbearing rotor, each including a support ring and one or more superhardbearing element(s). The superhard stator and rotor radial bearingelements each include respective superhard radial bearing surfaces thatare substantially opposed to one another. The superhard stator and rotorthrust-bearing surfaces may include diamond, while the superhard statorand rotor radial bearing surfaces may not include diamond, but includeanother superhard material (e.g., silicon carbide).

Embodiments of the invention also relate to methods of use in which abearing structure that does not include diamond is used with a generallyoppositely disposed other bearing structure that does include diamond,so that the bearing structure that does not include diamond wearspreferentially, and is replaced after a period of use. Thus a singlebearing structure (e.g., a rotor) that does include diamond may beemployed sequentially with a plurality of corresponding non-diamondbearing structures (e.g., stators) that wear preferentially, and arereplaced before the diamond bearing structure needs to be replaced.

For example, a bearing assembly may be provided, as described above, inwhich either the rotor or stator includes diamond, while the other ofthe rotor or stator does not include diamond, but includes anothersuperhard material (e.g., silicon carbide). After a period of use duringwhich the non-diamond bearing rotor or stator may wear preferentially,the non-diamond bearing rotor or stator may be replaced.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical or similar elements orfeatures in different views or embodiments shown in the drawings.

FIG. 1 is an isometric cutaway view of an embodiment of a thrust-bearingapparatus, which may employ differing materials for the bearing surfacesof the rotor and stator.

FIG. 2A is an isometric view of a thrust-bearing ring in which thebearing surface is a single substantially continuous surface.

FIG. 2B is an isometric cutaway view of an embodiment of athrust-bearing apparatus including the thrust-bearing ring of FIG. 2Awith an oppositely oriented thrust-bearing ring in which the bearingsurface is defined by a plurality of separate bearing elements so thatthe overall bearing surface is discontinuous.

FIG. 2C is an isometric cutaway view of an embodiment of athrust-bearing apparatus including two thrust-bearing rings similar tothat shown in FIG. 2A so that the bearing surface of the rotor andstator are each formed by a single substantially continuous bearingelement.

FIG. 3 is an isometric cutaway view of an embodiment of a radial bearingapparatus, which may employ differing materials for the bearing surfacesof the rotor and stator.

FIG. 4A is an isometric view of a radial bearing inner ring in which thebearing surface is a single substantially continuous surface.

FIG. 4B is an isometric view of a radial bearing outer ring in which thebearing surface is a single substantially continuous surface.

FIG. 4C is an isometric cutaway view of an embodiment of a radialbearing apparatus including the inner and outer radial bearing rings ofFIGS. 4A and 4B so that the bearing surface of the rotor and stator areeach formed by a single substantially continuous bearing element.

FIG. 4D is an isometric cutaway view of an embodiment of a radialbearing apparatus.

FIG. 4E is an isometric cutaway view of an embodiment of a radialbearing apparatus.

FIG. 5A is an isometric disassembled view of an embodiment of a bearingapparatus including both a thrust-bearing assembly and a radial bearingassembly, which may employ differing materials for one or more bearingsurfaces.

FIG. 5B is another isometric view of the bearing apparatus of FIG. 5A inan assembled configuration.

FIG. 6A is an isometric disassembled view of another embodiment of abearing apparatus in which the stator of the radial bearing assemblyincludes a single substantially continuous bearing element.

FIG. 6B is another isometric view of the bearing apparatus of FIG. 5A inan assembled configuration.

FIG. 7 is a schematic isometric cutaway view of a subterranean drillingsystem including one or more bearing apparatuses utilizing any of thedisclosed bearing apparatuses according to various embodiments.

DETAILED DESCRIPTION

Embodiments of the invention relate to bearing assemblies, bearingapparatuses, and methods of use in which one or more or at least aportion of one or more bearing surfaces of the rotor and/or the bearingsurfaces of the stator include different materials. For example, thebearing surface(s) of one of the rotor or stator may include diamond(e.g., polycrystalline diamond), while the bearing surface(s) of theother of the rotor or stator do not include diamond, but include anothersuperhard material (e.g., silicon carbide).

Another embodiment of the invention relates to bearing apparatusesincluding both a thrust-bearing assembly and a radial bearing assemblyin which the bearing surfaces of the thrust-bearing assembly includediamond, while the bearing surfaces of the radial bearing assembly donot include diamond, but include another superhard material.

The diamond bearing surfaces may be in the form of PCD, which may beattached to a substrate to form a PDC. For example, in any of theembodiments disclosed herein the bearing surfaces that employ PCD and/ora PDC may be formed and/or structured as disclosed in U.S. Pat. Nos.7,516,804; 7,866,418; 8,236,074; and 8,297,382; which are incorporatedherein, in their entirety, by this reference. PCD includes a pluralityof directly bonded together diamond grains exhibiting diamond-to-diamondbonding (e.g., sp³ bonding) therebetween, with a catalyst disposed in atleast a portion of the interstitial regions defined by the diamondgrains. In some embodiments, the catalyst may comprise a metal-solventcatalyst (e.g., cobalt, iron, nickel, or alloys thereof) or anonmetallic catalyst such as a carbonate catalyst. Furthermore, in anyof the bearing surfaces that use PCD, the catalyst used to form the PCD(e.g., cobalt) may be leached to a selected depth from the bearingsurface.

The diamond particles that are HPHT sintered to form the PCD used in thebearing elements disclosed herein may include one or more selected sizesthat may be determined, for example, by passing the diamond particlesthrough one or more sizing sieves or by any other method. In anembodiment, the plurality of diamond particles may include a relativelylarger size and at least one relatively smaller size. As used herein,the phrases “relatively larger” and “relatively smaller” refer toparticle sizes determined by any suitable method, which differ by atleast a factor of two (e.g., 40 μm and 20 μm). More particularly, invarious embodiments, the plurality of diamond particles may include aportion exhibiting a relatively larger size (e.g., 100 μm, 90 μm, 80 μm,70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 12 μm, 10 μm, 8 μm) andanother portion exhibiting at least one relatively smaller size (e.g.,30 μm, 20 μm, 10 μm, 15 μm, 12 μm, 10 μm, 8 μm, 4 μm, 2 μm, 1 μm, 0.5μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In an embodiment, theplurality of diamond particles may include a portion exhibiting arelatively larger size between about 40 μm and about 15 μm and anotherportion exhibiting a relatively smaller size between about 15 μm and 2μm. The plurality of diamond particles may also include three or moredifferent sizes (e.g., one relatively larger size and two or morerelatively smaller sizes) without limitation. The diamond grain size ofthe PCD so formed after HPHT sintering may be substantially the same orsimilar to the diamond particles used to form the PCD or the PCD of aPDC.

In an embodiment, other forms of diamond may also be employed, such asnatural diamond, other synthetic diamond, a diamond-silicon carbidecomposite as disclosed in U.S. Pat. No. 7,998,573 that is incorporatedherein in its entirety by this reference, diamond deposited by chemicalvapor deposition, diamond or diamond-like carbon deposited by physicalvapor deposition, or other deposition technique.

As used herein, a non-diamond superhard material employed for thenon-diamond bearing surface is a non-diamond material exhibiting ahardness that is at least as hard as tungsten carbide. Examples ofnon-diamond superhard materials include, but are not limited to,polycrystalline cubic boron nitride, silicon carbide, tungsten carbide,tantalum carbide, other carbides exhibiting a hardness at least equal tothat of tungsten carbide, or any combination of the foregoing.

The disclosed bearing apparatuses may be used in a number ofapplications, such as downhole motors in subterranean drilling systems,directional drilling systems, pumps, transmissions, gear boxes, and manyother applications.

FIG. 1 is an isometric cutaway view of an embodiment of a thrust-bearingapparatus 100, which may employ diamond bearing elements (e.g., PCDbearing elements) on one or both of the thrust-bearing assemblies 102 a,102 b. For example, any suitable PDC may be used as bearing elements. Anon-diamond superhard material may be employed for at least one of thebearing surfaces of at least one of the thrust-bearing assemblies. Forexample, one of the thrust-bearing assemblies 102 a, 102 b may includediamond bearing elements, while the other of the thrust-bearingassemblies 102 a, 102 b may include bearing elements using a non-diamondsuperhard material. Each thrust-bearing assembly 102 a, 102 b includesan annular support ring 104 a, 104 b that may be fabricated from anysuitable material, such as carbon steel, stainless steel, a superhardmaterial (e.g., silicon carbide, tantalum carbide, or another carbide),or another suitable material. In an embodiment, each support ring 104 a,104 b may include a plurality of pockets or recesses 105 that receives acorresponding bearing element 106 a, 106 b. For example, each bearingelement 106 a, 106 b may be mounted to a corresponding support ring 104a, 104 b within a corresponding recess by brazing, interference-fitting,using fasteners, or another suitable mounting technique. Alternatively,the bearing elements 106 a, 106 b may be mounted onto a surface ofsupport ring 104 a, 104 b, respectively, without being received into acorresponding recess.

In an embodiment, bearing elements 106 a mounted into or on support ring104 a may include a PCD bearing surface, while bearing elements 106 bmounted into or on support ring 104 b may not include diamond, butinclude bearing surfaces that include a superhard material other thandiamond (e.g., silicon carbide or another carbide or other ceramic). Forexample, bearing elements 106 a may comprise PDCs including a PCD table108 that may be metallurgically bonded to a substrate (e.g., a cementedcarbide substrate). In an embodiment, the substrate of bearing elements106 a to which PCD table 108 is bonded may comprise cobalt-cementedtungsten carbide or another suitable carbide material that may includechromium carbide, tantalum carbide, vanadium carbide, or combinationsthereof as an alternative to or in addition to tungsten carbide. EachPCD table 108 may include a bearing surface 110 a.

Bearing elements 106 b may include a non-diamond superhard material. Forexample, elements 106 b may be similarly shaped and sized as bearingelements 106 a, but do not include a PCD table thereon, the bearingsurface of bearing elements 106 b being defined rather by a non-diamondsuperhard material. For example, bearing elements 106 b may include acarbide, such as silicon carbide.

In use, bearing surfaces 110 a of thrust-bearing assembly 102 a bearagainst opposing bearing surfaces 110 b of the other bearing assembly102 b. For example, one of the thrust-bearing assemblies 102 a, 102 bmay be operably coupled to a shaft to rotate therewith and may be termeda “rotor.” The other of the thrust-bearing assemblies 102 a, 102 b maybe held stationary and may be termed a “stator.”

Because bearing surfaces 110 a and 110 b may include differentmaterials, non-diamond bearing surfaces may wear preferentially relativeto bearing surfaces includes diamond. Providing such a bearing assemblyincluding different material bearing surfaces may provide for betterheat transfer and better maintenance of a fluid film between bearingsurfaces 110 a and 110 b than if all bearing surfaces 110 a and 110 bincluded the same non-diamond superhard material (e.g., where bothinclude silicon carbide).

Diamond has substantially higher thermal conductivity than superhardcarbides, such as silicon carbide. Because one of bearing surfaces 110a, 110 b (e.g., 110 a) includes diamond, heat generated at non-diamondbearing surfaces may be better dissipated as a result of its proximityor contact with diamond bearing surfaces. Thus, a bearing assemblyincluding differing bearing surface materials, as described, may provideincreased wear resistance as compared to a bearing assembly in which allbearing surfaces include a non-diamond superhard material (e.g., siliconcarbide), but at significantly lower cost than would be associated witha bearing assembly in which both of the opposed bearing surfaces includeonly diamond.

In an embodiment, the stator may include at least one non-diamondsuperhard bearing surface, such as only including non-diamond bearingsurfaces. The stator within a bearing apparatus often fails before therotor. In some instances, this may occur because the stator bearingsurfaces are often subject to unequal heating and wear. For example,wear on a stator is often unequal as a result of a small number ofstator bearing elements being somewhat more “prominent” than the otherstator bearing elements. As a result, contact, heating, and wear duringuse may be preferentially associated with these more prominent statorbearing elements. For example, the bulk of the load and resulting wearmay be borne by, for example, the one to three most prominent bearingelements, while the other stator bearing elements may show little wearby comparison. Such wear may result from the difficulty of perfectlyaligning the bearing elements of the bearing assembly.

Because the stator may typically wear faster than the rotor, in anembodiment the stator bearing elements may not include diamond, butinclude a non-diamond superhard material, as the stator typically failsfirst anyway. In such embodiments, the stator may be replaced oncefailure or a given degree of wear occurs. In another embodiment, thestator may include at least one, one or more, or only diamond bearingsurfaces, and the rotor may not include or may only include a smallnumber of diamond bearing surfaces, such as including only non-diamondsuperhard material for bearing surfaces. It is currently believed thatthe configuration of thrust-bearing apparatus 100 facilitates fasterbreaking in of the bearing surfaces as the less hard bearing surfaceswear/break in relatively faster.

FIG. 2A shows a thrust-bearing assembly 202 b according to anotherembodiment. Thrust-bearing assembly 202 b includes a singlesubstantially continuous bearing surface 210 b defined by a singlesubstantially continuous bearing element 206 b rather than a pluralityof bearing elements. Such a configuration may improve wear performanceas compared to an assembly in which the overall bearing surface isformed of a plurality of segmented, discontinuous bearing surfacesdefined by the individual bearing elements. Wear performance may beimproved because alignment of a single, large substantially continuousbearing element may be more readily achieved than alignment of aplurality of discontinuous, spaced apart bearing elements. In addition,the substantial absence of any discontinuities in the overall bearingsurface (e.g., substantially planar in the context of the illustratedthrust-bearing assembly) may minimize and/or prevent chipping orcracking of substantially continuous bearing surface 210 b and/orpromote fluid film development.

FIG. 2B shows a bearing apparatus 100′ according to an embodiment, whichincludes the bearing assembly 202 b of FIG. 2A. Thus, one bearingassembly (e.g., assembly 202 b) may include a single substantiallycontinuous bearing surface (e.g., 210 b), while the generally oppositelydisposed bearing assembly (e.g., assembly 102 a) may include a pluralityof bearing elements, each defining a bearing surface (e.g., 110 a) sothat the overall ring-shaped bearing surface plane includes a pluralityof discontinuous, separate bearing surfaces. In an embodiment, bearingsurface 210 b of bearing assembly 202 b may not include diamond, butinclude a non-diamond superhard material while at least one of bearingsurfaces 110 a of bearing assembly 102 a include diamond.

As shown, in an embodiment, bearing surface 210 b and bearing element206 b may be provided integral with support ring 204 b. For example,bearing element 206 b and support ring 204 b may be formed of a singlepiece of the same material (e.g., a carbide, such as tantalum carbide,tungsten carbide, silicon carbide, vanadium carbide, boron nitride,titanium nitride, or combinations thereof).

FIG. 2C shows another bearing apparatus 100″ in which both bearingassemblies 202 a and 202 b each include a single substantiallycontinuous bearing surface 210 a and 210 b, respectively. In anembodiment, one of bearing surfaces 210 a or 210 b (e.g., 210 a) mayinclude diamond (e.g., polycrystalline diamond), while the other bearingsurface does not include diamond, but includes a non-diamond superhardmaterial. In an embodiment, at least a portion of bearing surfaces 210 aor 210 b (e.g., 210 a) may include diamond (e.g., polycrystallinediamond), while the other bearing surface does not include diamond butat least a portion of the bearing surface includes a non-diamondsuperhard material.

FIG. 3 is an isometric cutaway view of an embodiment of a radial bearingapparatus 300, which may employ different materials for at least aportion of the bearing surfaces of one or both of the assemblies inaccordance with the principles of any of the disclosed embodiments.Radial bearing apparatus 300 includes an inner race 302 positionedgenerally within an outer race 304. Outer race 304 includes one or morebearing elements 306 a mounted thereto that include respective bearingsurfaces 310 a. For such a radial bearing, bearing surface 310 a ofelements 306 a mounted to outer race 304 may be concavely curved. Innerrace 302 also includes a plurality of bearing elements 306 b affixedthereto that have respective bearing surfaces 310 b. For such a radialbearing, bearing surface 310 b of elements 306 b mounted to inner race302 may be convexly curved to correspond with the concave curvature ofbearing surface 310 a. The inner race 302 is positioned generally withinthe outer race 304 and, thus, the inner race 302 and outer race 304 maybe configured so that the bearing surfaces 310 a and 310 b may at leastpartially contact one another and move relative to each other as theinner race 302 and/or outer race 304 rotate relative to each otherduring use.

Either bearing elements 306 a or bearing elements 306 b may include adiamond (e.g., PCD) bearing surface, while one or both sets of bearingelements may include at least one bearing surface that includes asuperhard material other than diamond (e.g., silicon carbide). In anembodiment, bearing surfaces 310 b may include diamond (e.g.,polycrystalline diamond), while bearing surfaces 310 a may not includediamond, but include a non-diamond superhard material such as siliconcarbide or another type of diamond material such as a diamond-siliconcarbide composite. In an embodiment, outer race 304 may be a statorbearing assembly, while inner race 302 may be a rotor bearing assembly.In another embodiment, inner race 302 may be the stator, while outerrace 304 may be the rotor.

FIG. 4A shows an inner race 402 for use in a radial bearing apparatusaccording to another embodiment. Inner race 402 includes a bearingelement 406 b defining a single substantially continuous bearing surface410 b. As described above, such a configuration may improve wearperformance as compared to an assembly in which the overall bearingsurface is comprised of a plurality of segmented, discontinuous bearingsurfaces of the individual bearing elements and/or may promote fluidfilm development.

FIG. 4B shows an outer race 404 for use in a radial bearing apparatusaccording to another embodiment. Outer race 404 includes a bearingelement 406 a defining a single substantially continuous bearing surface410 a. Such a configuration may improve wear performance as compared toan assembly in which the overall bearing surface is comprised of aplurality of segmented, discontinuous bearing surfaces of the individualbearing elements and/or may promote fluid film development.

FIG. 4C shows an embodiment of a bearing apparatus 400 including innerrace 402 of FIG. 4A and the outer race 404 of FIG. 4B so that bothbearing elements 406 a and 406 b define substantially opposed bearingsurfaces 410 a and 410 b that are each a single substantially continuousbearing surface, without any discontinuities or segments disposedtherein. One of bearing surfaces 410 a, 410 b may include diamond (e.g.,PCD), while the other of the bearing surfaces does not include diamond,but includes a non-diamond superhard material (e.g., silicon carbide).In an embodiment, at least a portion of one or both of bearing surfaces410 a, 410 b may include diamond (e.g., PCD) and a non-diamond superhardmaterial (e.g., silicon carbide).

Various combinations of the illustrated inner and outer raceconfigurations may be employed in other embodiments. For example, FIG.4C shows a configuration in which both races each include a singlebearing element defining a substantially continuous bearing surface,which surfaces are oriented substantially opposite to one another duringuse. FIGS. 4D and 4E show configurations 400′ and 400″ according toadditional embodiments, in which either the inner race or outer raceincludes a single bearing element defining a substantially continuousbearing surface, while the other of the races includes a plurality ofbearing elements, such that the overall bearing surface (e.g.,resembling the inner or outer surface of a cylinder) is defined by aplurality of segmented or discontinuous bearing surfaces that areseparate from one another.

FIG. 4D shows a further embodiment of a radial bearing apparatus. Asshown, one bearing assembly (e.g., outer race 304) may include aplurality of bearing elements 306 a, each defining a separate bearingsurface 310 a, while the other bearing assembly (e.g., inner race 402)may include a single substantially continuous bearing element thatextends around substantially the entire perimeter of inner race 402, soas to define a single substantially continuous bearing surface 410 b. Inan embodiment, either bearing elements 306 a or bearing element 406 bcomprise diamond (e.g., bearing elements 306 a may comprise PCD or aPDC) while the other bearing element (e.g., bearing element 406 b) maynot comprise diamond, but comprises a non-diamond superhard material. Inan embodiment, at least a portion of the bearing element 406 b and/orthe bearing surface 410 b or the bearing elements 306 a may include PCD.

FIG. 4E shows a configuration similar to, but reversed, as compared toFIG. 4D. For example, outer race 404 includes a single substantiallycontinuous bearing element 406 a and bearing surface 410 a that extendsalong substantially the entire perimeter of outer race 404, while innerrace 302 (e.g., similar to that seen in FIG. 3) may include a pluralityof bearing elements 306 b, each defining a separate bearing surface 310b. Either bearing elements 306 b or bearing element 406 a includediamond (e.g., bearing elements 306 b may include diamond) while theother bearing element (e.g., bearing element 406 a) may not includediamond, but includes a non-diamond superhard material.

Any of the radial bearing apparatuses disclosed herein may be employedin a variety of mechanical applications, such as roller cone bits,downhole motors, and turbines. For example, so-called roller cone rotarydrill bits may benefit from a radial bearing apparatus. Morespecifically, the inner race may be mounted to a spindle of a rollercone and the outer race may be mounted to an inner bore formed within acone such that the outer race and inner race may be assembled to form aradial bearing apparatus.

FIGS. 5A and 5B show a bearing apparatus 500 that includes both athrust-bearing assembly and a radial bearing assembly, and which mayinclude one material (e.g., PCD) for the thrust-bearing surfaces, whileemploying a different material (e.g., a non-diamond superhard material)for at least another bearing surface such as the radial bearingsurfaces. In an embodiment, a portion of the thrust-bearing surfaces orradial bearing surfaces may include PCD and a portion of thethrust-bearing surfaces or radial bearing surfaces may include anon-diamond superhard material such as silicon carbide.

Bearing apparatus 500 includes a combination thrust/radial bearingassembly 501 that may include a thrust-bearing assembly 502 a and aradial bearing inner race 502. In an embodiment, combinationthrust/radial bearing assembly 501 may include a rotor, operativelycoupled to a shaft (e.g., received through inner race 502). Bearingapparatus 500 may further include thrust-bearing assembly 502 b andradial bearing outer race 504, which may operate as stator thrust andstator radial bearing components, respectively. Each thrust-bearingassembly 502 a and 502 b may include a respective support ring (e.g.,505 a and 505 b, respectively) with one or more bearing elements 506 aand 506 b mounted into or on the corresponding bearing ring.

Radial bearing inner race 502 of combination thrust/radial bearingassembly 501 includes one or more bearing elements 506 c, while radialbearing outer race 504 includes one or more bearing elements 506 dconfigured to be oriented in generally opposed orientation relative tobearing elements 506 c. Respective bearing surfaces defined by bearingelements 506 a, 506 b, 506 c, and 506 d may be selected, as describedabove, so that oppositely oriented bearing surfaces are different fromone another. For example, bearing elements 506 a or 506 b may includediamond, while the other does not include diamond, but includes anon-diamond superhard material. Similarly, bearing elements 506 c or 506d may include diamond, while the other does not include diamond, butincludes a non-diamond superhard material.

In another embodiment, both of thrust-bearing elements 506 a and 506 band their defined bearing surfaces may include one material (e.g.,diamond), while the radial bearing elements 506 c and 506 d and theirdefined bearing surfaces may include the other material (e.g., anon-diamond superhard material). In an embodiment, the thrust-bearingsurfaces may comprise diamond (e.g., PCD), while the radial bearingsurfaces do not comprise diamond, but include a non-diamond superhardmaterial such as silicon carbide. Such a configuration may be employedwhere the thrust load is considerably greater than the radial load sothat the diamond bearing surfaces employed in the thrust-bearing portionof the apparatus provide high wear resistance and thermal managementcharacteristics associated with the high thrust load. The radial bearingsurfaces may be non-diamond, allowing the apparatus to be fabricated atsignificantly lower cost than an embodiment where all bearing surfaceswere diamond, but also providing enhanced operation characteristics(e.g., greater wear resistance, improved heat transfer, or both) ascompared to an embodiment where all bearing surfaces were non-diamond.

FIGS. 6A and 6B show an apparatus 500′ similar to apparatus 500 of FIG.5A according to an embodiment, but in which radial bearing outer race504′ includes a single substantially continuous bearing element 506 d′rather than a plurality of separate bearing elements. Singlesubstantially continuous bearing element 506 d′ may extend substantiallyentirely about the inside perimeter of outer race 504′. As describedabove, where outer race 504′ serves as a stator to rotor inner race 502,the substantially continuous bearing surface may improve wear resistanceand operational life of stator outer race 504′.

Another embodiment (not shown) may replace one or both thrust-bearingassemblies 502 a and 502 b with configurations including a singlesubstantially continuous bearing element, rather than the illustratedconfiguration including a plurality of separate bearing elements.

Any of the embodiments for bearing apparatuses discussed above may beused in a subterranean drilling system. FIG. 7 is a schematic isometriccutaway view of a subterranean drilling system 700 according to anembodiment, which may employ one or more of any of the disclosed bearingapparatus embodiments. The subterranean drilling system 700 may includea housing 760 enclosing a downhole drilling motor 762 (i.e., a motor,turbine, or any other device capable of rotating an output shaft) thatmay be operably connected to an output shaft 756. A thrust-bearingapparatus 764 may be operably coupled to the downhole drilling motor762. The thrust-bearing apparatus 764 may be configured as any of thethrust-bearing apparatus embodiments disclosed herein. A rotary drillbit 768 may be configured to engage a subterranean formation and drill aborehole and may be connected to the output shaft 756. The rotary drillbit 768 is shown comprising a bit body 790 that includes radially andlongitudinally extending blades 792 with a plurality of PDCs 794 securedto the blades 792. However, other embodiments may utilize differenttypes of rotary drill bits, such as core bits and/or roller-cone bits.As the borehole is drilled, pipe sections may be connected to thesubterranean drilling system 700 to form a drill string capable ofprogressively drilling the borehole to a greater depth within the earth.

The thrust-bearing apparatus 764 may include a stator 772 that does notrotate and a rotor 774 that may be attached to the output shaft 756 androtates with the output shaft 756. As discussed above, thethrust-bearing apparatus 764 may be configured as any of the embodimentsdisclosed herein.

In operation, lubricating fluid may be circulated through the downholedrilling motor 762 to generate torque and rotate the output shaft 756and the rotary drill bit 768 attached thereto so that a borehole may bedrilled. A portion of the lubricating fluid may also be used tolubricate opposing bearing surfaces of the stator 772 and the rotor 774.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. For example, another embodiment may employPCD for one bearing surface, while employing a non-PCD superhardmaterial having a hardness lower than PCD for the opposing bearingsurface. In an embodiment, the superhard material may include a form ofdiamond exhibiting lower hardness than PCD (e.g., chemically vapordeposited diamond). Similar preferential wear characteristics may beassociated with such a configuration where the non-PCD bearing surfaceswear preferentially relative to the PCD bearing surfaces. Anotherembodiment may employ the harder PCD material for opposed thrust-bearingsurfaces while opposed radial bearing surfaces of a bearing apparatusmay not include PCD, but include a non-PCD superhard material having ahardness lower than PCD. Additionally, the words “including,” “having,”and variants thereof (e.g., “includes” and “has”) as used herein,including the claims, shall be open ended and have the same meaning asthe word “comprising” and variants thereof (e.g., “comprise” and“comprises”).

The invention claimed is:
 1. A method of forming a combinationthrust-bearing and radial bearing apparatus, the method comprising:positioning a superhard thrust-bearing surface of at least one superhardthrust-bearing element to be spaced from an axis of rotation by a firstdistance; and positioning a superhard radial bearing surface of at leastone superhard radial bearing element to be spaced from an axis ofrotation by a second distance that is less than the first distance. 2.The method of claim 1, further comprising at least one of: mounting theat least one superhard thrust-bearing element to a thrust-bearing statorsupport ring to form a thrust-bearing stator; mounting the at least onesuperhard thrust-bearing element to a thrust rotor support ring to forma thrust-bearing rotor; mounting the at least one superhard radialbearing element to a radial stator support ring to form a radial bearingstator; or mounting the at least one superhard radial bearing element toa radial rotor support ring to form a radial bearing rotor.
 3. Themethod of claim 2, further comprising: positioning the thrust-bearingstator adjacent to the thrust-bearing rotor; and positioning the radialbearing rotor within the radial bearing stator.
 4. The method of claim 2wherein the at least one superhard bearing element of one of thethrust-bearing stator or the thrust-bearing rotor includespolycrystalline diamond, and wherein the at least one superhard bearingelement of the other of the thrust-bearing stator or the thrust-bearingrotor includes at least one non-diamond superhard material.
 5. Themethod of claim 2 wherein one of the radial bearing stator or the radialbearing rotor includes polycrystalline diamond, and wherein the other ofthe radial bearing stator or the radial bearing rotor includes at leastone non-diamond superhard material.
 6. The method of claim 1, whereinthe superhard thrust-bearing surface of the at least one superhardthrust-bearing element includes polycrystalline diamond, and thesuperhard radial bearing surface of the at least one superhard radialbearing element includes at least one superhard material having ahardness that is lower than polycrystalline diamond.
 7. The method ofclaim 1 wherein the superhard thrust-bearing surface of the at least onesuperhard thrust-bearing element includes a superhard statorthrust-bearing surface, and wherein the superhard stator thrust-bearingsurface includes at least one non-diamond superhard material.
 8. Themethod of claim 1 wherein the superhard radial bearing surface of the atleast one superhard radial bearing element includes a superhard statorradial bearing surface, and wherein the superhard radial bearing surfaceincludes polycrystalline diamond.
 9. The method of claim 1 wherein atleast one of the superhard thrust-bearing element or the superhardradial bearing element includes a single continuous bearing surface. 10.The method of claim 1 wherein at least one of the superhardthrust-bearing element or the superhard radial bearing element includesa plurality of bearing elements.